Torque split type automatic transmission

ABSTRACT

A torque split type automatic transmission which transmits the torque output from an engine through two paths, adds the torque passing through and increased in each path, and outputs a final torque is provided, wherein the torque of the engine is divided into two portions by a torque split device and each portion of the torque is transmitted respectively to first and second power delivery paths, wherein the first power delivery path is directly connected to a driving wheel, and wherein the second power delivery path is provided with a launching device and a transmission device disposed in series so as to increase the torque, and output of the second power delivery path is added to the torque of the first power delivery path to output the final torque.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2009-0113501 filed in the Korean Intellectual Property Office on Nov.23, 2009, the entire contents of which is incorporated herein for allpurposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a torque split type automatictransmission which is applied to vehicles. More particularly, thepresent invention relates to a torque split type automatic transmissionwhich increases torque by transmitting the torque output from an enginethrough two paths and adding the torque passing through each path.

2. Description of Related Art

Recently, engine output increases by 20-30% compared with a conventionalengine with the same exhaust amount and size due to development ofengine technologies.

Since a conventional transmission includes only one power delivery path,all the torque of the engine is directly transmitted to a launchingdevice such as a torque converter or a clutch. Therefore, if the engineoutput increases, design of the transmission must be changed so as toincrease torque delivery capacity.

In order to increase the torque delivery capacity, strength of an axlemust be strengthened and the number of friction members must beincreased due to characteristics of a power delivery device. However, ifthe strength of the axle is strengthened, weight of the axle should beincreased. In addition, if the number of the friction members isincreased, size of the transmission should be increased. Therefore, fuelconsumption and power performance of a vehicle may be deteriorated dueto increase in the weight of the axle and installability of thetransmission may be deteriorated due to increase in the size of thetransmission.

Since it is needed to change a design of the launching device such asthe torque converter in order to increase torque capacity thereof, muchdevelopment cost and time is needed.

Recently, a torque split type transmission which transmits the torquethrough at least two power delivery paths is developing. The torquesplit type transmission has a merit that the torque capacity canincrease with a few changes in the design.

Some examples of the torque split type transmission are described inU.S. Pat. Nos. 4,014,223, 4,117,745, and 4,226,123 having a powerdelivery path shown in FIG. 6A and in U.S. Pat. No. 5,201,692 having apower delivery path shown in FIG. 6B.

The torque split type transmission shown in FIG. 6A includes a firstpath in which the engine torque is indirectly delivered to atransmission device 112 through a planetary gear set which is a torquesplit device 110 and a torque converter which is a launching device 111and a second path in which the engine torque is directly delivered fromthe planetary gear set 110 to the transmission device 112. The torqueincreased in the torque converter which is the launching device 111 isadded to the torque transmitted from the torque split device 110 to thetransmission device 112, and final torque is output to a driving wheelthrough the transmission device 112.

According to the torque split type transmission shown in FIG. 6B, theengine is increased in the torque converter which is the launchingdevice 120. After that, the torque is dividedly delivered to the drivingwheel through the planetary gear set of the torque split device 121 andto a continuously variable transmission of the transmission device 122.The torque output from the transmission device 122 is added to thetorque delivered from the torque split device 121 to the driving wheel.

According to the torque split type transmission shown in FIG. 6A, allthe increased torque is delivered to the transmission device and it maycause problems in the torque delivery capacity of the transmissiondevice.

According to the torque split type transmission shown in FIG. 6B, thecontinuously variable transmission is used as the transmission device.If large torque is delivered to the continuously variable transmission,torque split efficiency may be deteriorated.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY OF THE INVENTION

Various aspects of the present invention are directed to provide atorque split type automatic transmission having advantages of reducingtorque delivered to a launching device and a transmission device bydelivering the torque from an engine through two paths. Therefore,torque delivery capacity and size of the torque split type automatictransmission may not be increased according to the present invention.

In an aspect of the present invention, the torque split type automatictransmission which transmits the torque output from an engine throughtwo paths, adds the torque passing through and increased in each path,and outputs a final torque, is provided, wherein the torque of theengine is divided into two portions by a torque split device and eachportion of the torque is transmitted respectively to first and secondpower delivery paths, wherein the first power delivery path is directlyconnected to a driving wheel, and wherein the second power delivery pathis provided with a launching device and a transmission device disposedin series so as to increase the torque, and output of the second powerdelivery path is added to the torque of the first power delivery path tooutput the final torque.

The torque split device may include a single pinion planetary gear setsuch that one rotational element of three rotational elements isoperated as an input element receiving the torque of the engine, and theother two rotational elements are operated as output elements by beingconnected respectively to the first and second power delivery paths.

The torque transmitted through the first power delivery path may belarger than the torque transmitted through the second power deliverypath.

The launching device disposed in the second power delivery path may be atorque converter.

The transmission device disposed in the second power delivery path maybe a multiple-shift transmission device comprising a plurality ofplanetary gear sets, clutches, and brakes.

In another aspect of the present invention, the torque split typeautomatic transmission which transmits the torque output from an enginethrough two paths, adds the torque passing through and increased in eachpath, and outputs a final torque, may include a torque split devicecomprising a planetary gear set which receives the torque of the engine,divides the torque into two portions, and transmits the two portions ofthe torque respectively to first and second power delivery paths, afirst power delivery shaft engaged to the torque split device to formthe first power delivery path and provided with a first output gear, alaunching device being a torque converter, engaged to the torque splitdevice, disposed in the second power delivery path, and converting thetorque transmitted to the second power delivery path to output a firsttorque, a transmission device disposed at a downstream of the launchingdevice in the second power delivery path to receive the first torque,performing multiple-shift, and provided with a second output gear tooutput a second torque, and a transfer shaft engaged respectively withthe first and second output gears, adding the torque transmitted throughthe first power delivery path and the second torque of the transmissiondevice, and finally outputting the final torque.

The torque split device may include a single pinion planetary gear setand is disposed in the torque converter which is the launching device.

The torque split device may include a sun gear, a planet carrier, and aring gear as rotational elements thereof, wherein the planet carrier isdirectly connected to an output shaft of the engine so as to be operatedas an input element, the ring gear is connected to the first powerdelivery shaft forming the first power delivery path, and the sun gearis connected to an impeller of the torque converter through a connectingmember and is connected to a turbine through a lock-up clutch so as toform the second power delivery path.

The connecting member may be selectively connected to a front cover ofthe torque converter directly connected to the output shaft of theengine by interposing a direct-coupling clutch.

The transmission device may include first and second planetary gear setsbeing single pinion planetary gear sets, wherein the first planetarygear set comprises a first sun gear, a first planet carrier, and a firstring gear as rotational elements thereof, and the second planetary gearset comprises a second sun gear, a second planet carrier, and a secondring gear as rotational elements thereof.

The first planet carrier may be directly connected to the second ringgear and the first ring gear is directly connected to the second planetcarrier such that the first sun gear is a first rotational element, thefirst planet carrier and the second ring gear are a second rotationalelement, the first ring gear and the second planet carrier are a thirdrotational element, and the second sun gear is a fourth rotationalelement, wherein the first rotational element is selectively connectedto the second power delivery shaft connected to a turbine by interposinga first clutch, wherein the third rotational element is selectivelyconnected to the second power delivery shaft by interposing a secondclutch and is selectively connected to a transmission housing byinterposing a first brake disposed in parallel with an one-way clutch,wherein the fourth rotational element is selectively connected to thesecond power delivery shaft by interposing a third clutch and isselectively connected to the transmission housing by interposing asecond brake, and wherein the second rotational element is connected tothe second output gear and is operated as an output element to outputthe second torque.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description of the Invention, which togetherserve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for explaining concept of the presentinvention.

FIG. 2 is a schematic diagram for explaining operation of a torque splitdevice applicable to the present invention.

FIG. 3 is a schematic diagram of a torque split type automatictransmission according to an exemplary embodiment of the presentinvention.

FIG. 4 is an operational chart for a transmission device according to anexemplary embodiment of the present invention.

FIG. 5 is a lever diagram for a transmission device according to anexemplary embodiment of the present invention.

FIGS. 6A and 6B are block diagrams showing power delivery path of theconventional art.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram for explaining concept of the presentinvention.

As shown in FIG. 1, torque of the engine is divided into two portions ata torque split device 2, and each portion of the torque is deliveredrespectively through first and second power delivery paths PT1 and PT2according to an exemplary embodiment of the present invention. The firstpower delivery path PT1 is directly connected to a driving wheel, and alaunching device 4 and a transmission device 6 which are devices forincreasing the torque are disposed in series in the second powerdelivery path PT2. Output side of the second power delivery path PT2meets the first power delivery path PT1.

The torque split device 2 includes a single pinion planetary gear set.One rotational element of three rotational elements is operated as aninput element receiving the torque of the engine, and another tworotational elements are connected respectively to the first and secondpower delivery path PT1 and PT2. A double pinion planetary gear set maybe used as the torque split device 2.

In addition, a torque converter is mainly used as the launching device4. The launching device 4 increases the torque input through the secondpower delivery path PT2 and delivers the increased torque to thetransmission device 6. A multiple-shift transmission applied to aconventional automatic transmission is used as the transmission device6. The transmission device 6 increases the torque through shifting andoutputs the torque. It is exemplarily described in this specificationthat a multiple-shift transmission realizing four forward speeds and onereverse speed is used as the transmission device 6, but it is well knownto a person of an ordinary skill in the art that other multiple-shifttransmissions with different structure from the exemplary embodiment ofthe present invention may be used.

The torque delivered from the torque split device 2 to the second powerdelivery path PT2 is increased when passing through the launching device4 and the transmission device 6, and is added to the torque of the firstpower delivery path PT1. After that, the torque is output through adriving wheel.

More concretely, in a state that a planet carrier PC of the planetarygear set being the torque split device 2 is operated as an inputelement, a sun gear S is connected to the second power delivery path PT2and a ring gear R is connected to the first power delivery path PT1. Therotational elements of the planetary gear set connected respectively tothe input element and the first and second power delivery paths PT1 andPT2 may be changed. However, so as to deliver the small torque to thesecond power delivery path PT2, it is preferable for the planetary gearset to have the same connection relationship as the exemplary embodimentof the present invention due to operating characteristics of theplanetary gear set.

If we assume that a planetary gear ratio of the planetary gear set is 3(that is, 3:1) and engine torque Te output from the engine is 100 asshown in FIG. 2, the engine torque Te is divided into a ratio of 1:3 andeach torque is delivered respectively to the sun gear S and the ringgear R. Therefore, torque Ts of the sun gear is 25 and torque Tr of thering gear is 75.

If we assume that torque converting ratio of the launching device 4 is 2and gear ratio of the transmission device is 3, the torque Te (=25) ofthe sun gear input to the launching device 4 through the second powerdelivery path PT2 is doubled to 50 by the torque converting ratio andthe torque (=50) is input to the transmission device 6. After that, thetorque (=50) is tripled to 150 by the gear ratio. After that, the torque(=150) of the second power delivery path PT2 output from thetransmission device 6 is added to the torque (=75) of the first powerdelivery path PT1 at a node (Node 1), and the final torque (=225) isdelivered to the driving wheel.

In this case, since the torque applied to the launching device 4 and thetransmission device 6 disposed on the second power delivery path PT2 issmall, design capacity (diameter of a shaft, thickness of a case, sizeand the number of clutch) of the components used in the launching device4 and the transmission device 6 may be smaller than that of thecomponents used in a conventional transmission device 6. Accordingly,size of the transmission can be reduced.

The concept of the present invention is exemplarily described assumingthe planetary gear ratio is 3, the torque converting ratio of the torqueconverter is 2, and the gear ratio is 3. If three ratios change,division ratio and increase ratio of the torque also change. Therefore,three ratios may be set considering a maximum speed of a vehicle.

FIG. 3 is a schematic diagram of a torque split type automatictransmission according to an exemplary embodiment of the presentinvention.

According to a torque split type automatic transmission shown in FIG. 3,the planetary gear set PG of the torque split device 2 is formedintegral with the torque converter T/C of the launching device 4.

The planetary gear set PG is mounted in the torque converter T/C in thedrawings, but planetary gear set PG may be mounted at the exterior ofthe torque converter T/C.

The planetary gear set PG of the torque split device 2 is a singlepinion planetary gear set, and includes three rotational elements, thatis, the sun gear S, the planet carrier PC, and the ring gear R.

In addition, the torque converter T/C of the launching device 4 includesa front cover 10 connected to a crankshaft of the engine and rotates, animpeller 12 connected to one rotational element of the planetary gearset PG, a turbine 14 facing the impeller 12, and a stator 16 disposedbetween the impeller 12 and the turbine 14 and delivering automatictransmission oil flowing out from the turbine 14 to the impeller 12after changing flowing direction of the automatic transmission oil.

In order to couple the planetary gear set PG to the torque converterT/C, the planetary gear set PG is disposed between the front cover 10and the turbine 12, the planet carrier PC as well as the front cover 10is connected to an output shaft EOS of the engine, the sun gear S isdirectly connected to the impeller 12 and is selectively connected tothe turbine 14 by interposing a lock-up clutch L/C therebetween, and thering gear R is connected to a first output gear 20 through a first powerdelivery shaft 18 extended rearward (opposite side of the engine).

In addition, the front cover 10 is connected to a connecting member 22connecting the sun gear S with the impeller 12 by interposing adirect-coupling clutch E/C therebetween, and a rear end of the frontcover 10 is directly connected to a hydraulic pump O/P.

The lock-up clutch L/C selectively couples the impeller 12 with theturbine 14, and the direct-coupling clutch E/C makes the planetary gearset PG becomes a locked state so as to directly couple the output shaftEOS of the engine with the power delivery shaft 18.

If the engine torque is input through the front cover 10 and the planetcarrier PC, ¼ of the engine torque is input to the torque converter T/Cthrough the sun gear S and ¾ of the engine torque is delivered to thefirst power delivery shaft 18 when assuming the planetary gear ratio is3.

In addition, the torque input to the torque converter T/C is increasedand is transmitted to the transmission device 6. Any type oftransmissions which enables of shifting may be used as the transmissiondevice 6. In this specification, a transmission realizing four forwardspeeds and one reverse speed is exemplified, but the transmission device6 is not limited to this.

The transmission device 6 includes first and second planetary gear setsPG1 and PG2 being single pinion planetary gear sets. A first planetcarrier PC1 is directly connected to a second ring gear R2 and a firstring gear R1 is directly connected to a second planet carrier PC2 suchthat the transmission device 6 has four rotational elements N1, N2, N3,and N4.

Accordingly, a first sun gear S1 is set as a first rotational elementN1, the first planet carrier PC1 and the second ring gear R2 are set asa second rotational element N2, the first ring gear R1 and the secondplanet carrier PC2 are set as a third rotational element N3, and asecond sun gear S2 is set as a fourth rotational element N4.

In addition, the first sun gear S1 of the first rotational element N1 isselectively connected to the turbine 14 through a second power deliveryshaft 24 such that the torque of the turbine 14 is selectivelytransmitted to the first sun gear S1. A first clutch C1 is interposedbetween the second power delivery shaft 24 and the first sun gear S1.

The second planet carrier PC2 forming the third rotational element N3 isselectively connected to the second power delivery shaft 24 through asecond clutch C2 and is selectively connected to a transmission housingH through a first brake B1 disposed in parallel with a one-way clutch F.

In addition, the second sun gear S2 forming the fourth rotationalelement N4 is selectively connected to the second power delivery shaft24 through a third clutch C3 and is selectively connected to thetransmission housing H through a second brake B2, and the first planetcarrier PC1 forming the second rotational element N2 is directlyconnected to a second output gear 26 and is always operated as an outputelement.

As shown in FIG. 4, the clutches C1, C2, and C3 and the brakes B1 and B2are selectively operated at each shift-speed.

The first clutch C1 and the first brake B1 are operated at a firstforward speed D1, the first clutch C1 and the second brake B2 areoperated at a second forward speed D2, the first and second clutches C1and C2 are operated at a third forward speed D3, the second clutch C2and the second brake B2 are operated at a fourth forward speed D4, andthe third clutch C3 and the first brake B1 are operated at a reversespeed REV.

In this specification, it is described that the first clutch C1 and thefirst brake B1 are operated at the first forward speed D1. However, in acase that first brake B1 is disposed in parallel with the one-way clutchFIG. 2, the first brake B1 is not operated but the one-way clutch F isoperated at the first speed in D range so as to improve shift feel whenshifting to the second speed.

FIG. 5 is a lever diagram for a transmission device according to anexemplary embodiment of the present invention.

In FIG. 5, a lower horizontal line represents a rotational speed is “0”,and an upper horizontal line represents a rotation speed is “1.0”, thatis, the rotational speed thereof is the same as that of the second powerdelivery shaft 24.

Four vertical lines in FIG. 5 represent the first sun gear S1 of thefirst rotational element N1, the first planet carrier PC1 and the secondring gear R2 of the second rotational element N2, the first ring gear R1and the second planet carrier PC2 of the third rotational element N3,and the second sun gear S2 of the fourth rotational element N4sequentially from the left, and distances therebetween are set accordingto gear ratios of the first and second planetary gear set PG1 and PG2(teeth number of the sun gear/teeth number of the ring gear).

Position of each rotation element in the lever diagram is well known toa person of an ordinary skill in the art who designs a gear train, andthus detailed description will be omitted.

[First Forward Speed]

As shown in FIG. 4, the first clutch C1 and the first brake B1 areoperated at the first forward speed D1.

In a state that the torque of the second power delivery shaft 24 isinput to the first rotational element N1 by an operation of the firstclutch C1, the third rotational element N3 is operated as a fixedelement by an operation of the first brake B1 such that a first shiftline SP1 is formed. Therefore, the first forward speed D1 is outputthrough the second rotational element N2 which is the output element.

[Second Forward Speed]

The first brake B1 which is operated at the first forward speed D1 isreleased, and the second brake B2 is operated at the second forwardspeed D2.

In a state that the torque of the second power delivery shaft 24 isinput to the first rotational element N1 by the operation of the firstclutch the fixed element is changed from the third rotational element N3to the fourth rotational element N4 by an operation of the second brakeB2 such that a second shift line SP2 is formed. Therefore, the secondforward speed D2 is output through the second rotational element N2which is the output element.

[Third Forward Speed]

As shown in FIG. 4, the second brake B2 which is operated at the secondforward speed D2 is released, and the second clutch C2 is operated atthe third forward speed D3.

In a state that the torque of the second power delivery shaft 24 isinput to the first rotational element N1 by the operation of the firstclutch C1, the torque of the second power delivery shaft 24 is alsoinput to the third rotational element N3 by an operation of the secondclutch C2 such that the first and second planetary gear sets PG1 and PG2become direct-coupling states and a third shift line SP3 is formed.Therefore, the third forward speed D3, the rotational speed of which isthe same as that of the second power delivery shaft 24, is outputthrough the second rotational element N2 which is the output element.

[Fourth Forward Speed]

As shown in FIG. 4, the first clutch C1 which is operated at the thirdforward speed D3 is released, and the second brake B2 is operated at thefourth forward speed D4.

In a state that the torque of the second power delivery shaft 24 isinput to the third rotational element N3 by the operation of the secondclutch C2, the fourth rotational element N4 is operated as the fixedelement by the operation of the second brake B2 such that a fourth shiftline SP4 is formed. Therefore, the fourth forward speed D4 is outputthrough the second rotational element N2 which is the output element.

[Reverse Speed]

As shown in FIG. 4, the first brake B1 and the third clutch C3 areoperated at the reverse speed REV.

In a state that the torque of the second power delivery shaft 24 isinput to the fourth rotational element N4 by an operation of the thirdclutch C3, the third rotational element N3 is operated as the fixedelement by the operation of the first brake B1 such that a reverse shiftline SR is formed. Therefore, the reverse speed REV is output throughthe second rotational element N2 which is the output element.

The torque increased during a shifting is output through the secondoutput gear 26 and the torque of the first power delivery shaft 18 isoutput through the first output gear 20. The torque of the second outputgear 26 and the torque of the first output gear 20 at the first powerdelivery shaft 18 are added at a transfer shaft 28 forming a node, andthe final torque is output to the driving wheel through a differentialapparatus (not shown).

As described above, the torque transmitted from the engine is dividedinto two portions by the planetary gear set PG of the torque splitdevice 2, and a portion of the torque is transmitted to the sun gear S.The portion of the torque is transmitted to the transmission apparatus 6through the torque converter T/C and is increased during the shiftingoccurring by the operations of the clutches C1, C2, and C3 and thebrakes B1 and B2. After that, the portion of the torque is transmittedto the transfer shaft 28.

In addition, the other portion of the torque is transmitted through thefirst power delivery shaft 18 and is added to the portion of the torquetransmitted from the transmission apparatus 6.

At this time, the transfer shaft 28 receives the torques with differentrotational speed respectively from the first and second output gears 20and 26, but can add the torques transmitted through two paths bycomplementary operation of the torque split device 2 and the launchingdevice 4 which are not compete rigid body.

A portion of torque divided by a torque split device is transmitted tothe second power delivery path and is increased during passing through alaunching device and a transmission device. Then, the portion of thetorque is added to the other portion of torque transmitted through thefirst power delivery path, and a final torque is output.

At this time, the portion of the torque transmitted from the torquesplit device to the second power delivery path is smaller than the otherportion of the torque transmitted to the first power delivery path, andis increased during passing through the launching device and thetransmission device.

Since the torque applied to the launching device and the transmissiondevice disposed on the second power delivery path is small, designcapacity (diameter of a shaft, thickness of a case, size and the numberof clutch) of the components used in the launching device and thetransmission device may be smaller than that of the components used in aconventional transmission device. Accordingly, size of the transmissioncan be reduced.

For convenience in explanation and accurate definition in the appendedclaims, the terms “front” and “rear” are used to describe features ofthe exemplary embodiments with reference to the positions of suchfeatures as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described in orderto explain certain principles of the invention and their practicalapplication, to thereby enable others skilled in the art to make andutilize various exemplary embodiments of the present invention, as wellas various alternatives and modifications thereof. It is intended thatthe scope of the invention be defined by the Claims appended hereto andtheir equivalents.

What is claimed is:
 1. A torque split type automatic transmission whichtransmits a torque output from an engine through two paths, adds eachtorque passing through and being increased in each path, and outputs afinal torque, wherein the torque of the engine is divided into twoportions by a torque split device and each portion of the torque istransmitted respectively to first and second power delivery paths of thetwo paths, wherein the first power delivery path is operably connectedto a driving wheel via a transfer shaft, wherein the second powerdelivery path is provided with a launching device and a transmissiondevice disposed in series so as to increase the torque passing throughthe second power delivery path, and output of the transmission device onthe second power delivery path is directly added to the torque of thefirst power delivery path via the transfer shaft to output the finaltorque, and wherein the torque split device is not directly connected tothe transmission device, and wherein the first power delivery pathcompletely bypasses the launching device and the transmission device tothe transfer shaft.
 2. The torque split type automatic transmission ofclaim 1, wherein the torque split device comprises a single pinionplanetary gear set such that one rotational element of three rotationalelements is operated as an input element receiving the torque of theengine, and the other two rotational elements are operated as outputelements by being connected respectively to the first and second powerdelivery paths.
 3. The torque split type automatic transmission of claim2, wherein the torque transmitted through the first power delivery pathis larger than the torque transmitted through the second power deliverypath.
 4. The torque split type automatic transmission of claim 1,wherein the launching device disposed in the second power delivery pathis a torque converter.
 5. The torque split type automatic transmissionof claim 1, wherein the transmission device disposed in the second powerdelivery path is a multiple-shift transmission device comprising aplurality of planetary gear sets, clutches, and brakes.
 6. A torquesplit type automatic transmission which transmits a torque output froman engine through two paths, adds each torque passing through andincreased in each path of the two paths, and outputs a final torque, thetorque split type automatic transmission comprising: a torque splitdevice comprising a planetary gear set which receives the torque of theengine, divides the torque into two portions, and transmits the twoportions of the torque respectively to first and second power deliverypaths of the two paths; a first power delivery shaft engaged to thetorque split device to form the first power delivery path and providedwith a first output gear; a launching device being a torque converter,engaged to the torque split device, disposed in the second powerdelivery path, and converting the torque transmitted to the second powerdelivery path to output a first torque; a transmission device disposeddownstream of the launching device in the second power delivery path toreceive the first torque, performing multiple-shift, and provided with asecond output gear to output a second torque; and a transfer shaftengaged respectively with the first and second output gears, directlyadding the torque transmitted through the first power delivery path andthe second torque of the transmission device, and finally outputting thefinal torque, wherein the torque split device is not directly connectedto the transmission device, and wherein the first power delivery pathcompletely bypasses the launching device and the transmission device tothe transfer shaft.
 7. The torque split type automatic transmission ofclaim 6, wherein the torque split device comprises a single pinionplanetary gear set and is disposed in the torque converter which is thelaunching device.
 8. The torque split type automatic transmission ofclaim 7, wherein the torque split device comprises a sun gear, a planetcarrier, and a ring gear as rotational elements thereof, and wherein theplanet carrier is directly connected to an output shaft of the engine soas to be operated as an input element, the ring gear is connected to thefirst power delivery shaft forming the first power delivery path, andthe sun gear is connected to an impeller of the torque converter througha connecting member and is connected to a turbine through a lock-upclutch so as to form the second power delivery path.
 9. The torque splittype automatic transmission of claim 8, wherein the connecting member isselectively connected to a front cover of the torque converter directlyconnected to the output shaft of the engine by interposing adirect-coupling clutch.
 10. The torque split type automatic transmissionof claim 6, wherein the transmission device comprises first and secondplanetary gear sets being single pinion planetary gear sets, and whereinthe first planetary gear set comprises a first sun gear, a first planetcarrier, and a first ring gear as rotational elements thereof, and thesecond planetary gear set comprises a second sun gear, a second planetcarrier, and a second ring gear as rotational elements thereof.
 11. Thetorque split type automatic transmission of claim 10, wherein the firstplanet carrier is directly connected to the second ring gear and thefirst ring gear is directly connected to the second planet carrier suchthat the first sun gear is a first rotational element, the first planetcarrier and the second ring gear are a second rotational element, thefirst ring gear and the second planet carrier are a third rotationalelement, and the second sun gear is a fourth rotational element, whereinthe first rotational element is selectively connected to the secondpower delivery shaft connected to a turbine by interposing a firstclutch, wherein the third rotational element is selectively connected tothe second power delivery shaft by interposing a second clutch and isselectively connected to a transmission housing by interposing a firstbrake disposed in parallel with an one-way clutch, wherein the fourthrotational element is selectively connected to the second power deliveryshaft by interposing a third clutch and is selectively connected to thetransmission housing by interposing a second brake, and wherein thesecond rotational element is connected to the second output gear and isoperated as an output element to output the second torque.